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Klemenzdottir EO, Arnadottir GA, Jensson BO, Jonasdottir A, Katrinardottir H, Fridriksdottir R, Jonasdottir A, Sigurdsson A, Gudjonsson SA, Jonsson JJ, Stefansdottir V, Danielsen R, Palsdottir A, Jonsson H, Helgason A, Magnusson OT, Thorsteinsdottir U, Bjornsson HT, Stefansson K, Sulem P. A population-based survey of FBN1 variants in Iceland reveals underdiagnosis of Marfan syndrome. Eur J Hum Genet 2024; 32:44-51. [PMID: 37684520 PMCID: PMC10772070 DOI: 10.1038/s41431-023-01455-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2022] [Revised: 08/18/2023] [Accepted: 08/30/2023] [Indexed: 09/10/2023] Open
Abstract
Marfan syndrome (MFS) is an autosomal dominant condition characterized by aortic aneurysm, skeletal abnormalities, and lens dislocation, and is caused by variants in the FBN1 gene. To explore causes of MFS and the prevalence of the disease in Iceland we collected information from all living individuals with a clinical diagnosis of MFS in Iceland (n = 32) and performed whole-genome sequencing of those who did not have a confirmed genetic diagnosis (27/32). Moreover, to assess a potential underdiagnosis of MFS in Iceland we attempted a genotype-based approach to identify individuals with MFS. We interrogated deCODE genetics' database of 35,712 whole-genome sequenced individuals to search for rare sequence variants in FBN1. Overall, we identified 15 pathogenic or likely pathogenic variants in FBN1 in 44 individuals, only 22 of whom were previously diagnosed with MFS. The most common of these variants, NM_000138.4:c.8038 C > T p.(Arg2680Cys), is present in a multi-generational pedigree, and was found to stem from a single forefather born around 1840. The p.(Arg2680Cys) variant associates with a form of MFS that seems to have an enrichment of abdominal aortic aneurysm, suggesting that this may be a particularly common feature of p.(Arg2680Cys)-associated MFS. Based on these combined genetic and clinical data, we show that MFS prevalence in Iceland could be as high as 1/6,600 in Iceland, compared to 1/10,000 based on clinical diagnosis alone, which indicates underdiagnosis of this actionable genetic disorder.
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Affiliation(s)
| | - Gudny Anna Arnadottir
- deCODE Genetics/Amgen, Inc., Reykjavik, Iceland
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
| | | | | | | | | | | | | | | | - Jon Johannes Jonsson
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- Department of Genetics, Landspitali Universtity Hospital, Reykjavik, Iceland
| | | | - Ragnar Danielsen
- Department of Cardiology, Landspitali University Hospital, Reykjavik, Iceland
| | - Astridur Palsdottir
- Institute for Experimental Pathology at Keldur, University of Iceland, Reykjavik, Iceland
| | | | - Agnar Helgason
- deCODE Genetics/Amgen, Inc., Reykjavik, Iceland
- Department of Anthropology, University of Iceland, Reykjavik, Iceland
| | | | - Unnur Thorsteinsdottir
- deCODE Genetics/Amgen, Inc., Reykjavik, Iceland
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
| | - Hans Tomas Bjornsson
- Department of Pediatrics, Landspitali University Hospital, Reykjavik, Iceland
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland
- Department of Genetics, Landspitali Universtity Hospital, Reykjavik, Iceland
- McKusick-Nathans Institute of Genetic Medicine, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
| | - Kari Stefansson
- deCODE Genetics/Amgen, Inc., Reykjavik, Iceland.
- Faculty of Medicine, University of Iceland, Reykjavik, Iceland.
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Stefansdottir V, Skirton H, Johannsson OT, Olafsdottir H, Olafsdottir GH, Tryggvadottir L, Jonsson JJ. Electronically ascertained extended pedigrees in breast cancer genetic counseling. Fam Cancer 2018; 18:153-160. [PMID: 30251169 DOI: 10.1007/s10689-018-0105-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
A comprehensive pedigree, usually provided by the counselee and verified by medical records, is essential for risk assessment in cancer genetic counseling. Collecting the relevant information is time-consuming and sometimes impossible. We studied the use of electronically ascertained pedigrees (EGP). The study group comprised women (n = 1352) receiving HBOC genetic counseling between December 2006 and December 2016 at Landspitali in Iceland. EGP's were ascertained using information from the population-based Genealogy Database and Icelandic Cancer Registry. The likelihood of being positive for the Icelandic founder BRCA2 pathogenic variant NM_000059.3:c.767_771delCAAAT was calculated using the risk assessment program Boadicea. We used this unique data to estimate the optimal size of pedigrees, e.g., those that best balance the accuracy of risk assessment using Boadicea and cost of ascertainment. Sub-groups of randomly selected 104 positive and 105 negative women for the founder BRCA2 PV were formed and Receiver Operating Characteristics curves compared for efficiency of PV prediction with a Boadicea score. The optimal pedigree size included 3° relatives or up to five generations with an average no. of 53.8 individuals (range 9-220) (AUC 0.801). Adding 4° relatives did not improve the outcome. Pedigrees including 3° relatives are difficult and sometimes impossible to generate with conventional methods. Pedigrees ascertained with data from pre-existing genealogy databases and cancer registries can save effort and contain more information than traditional pedigrees. Genetic services should consider generating EGP's which requires access to an accurate genealogy database and cancer registry. Local data protection laws and regulations have to be addressed.
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Affiliation(s)
- V Stefansdottir
- Department of Genetics and Molecular Medicine, Landspitali - National University Hospital, Hringbraut, 101, Reykjavik, Iceland.,Department of Biochemistry and Molecular Biology, Univ. of Iceland, Reykjavik, Iceland
| | - H Skirton
- Faculty of Health and Human Sciences, Plymouth University, Plymouth, UK
| | - O Th Johannsson
- Department Of Medical Oncology, Landspitali - National University Hospital, Reykjavik, Iceland
| | - H Olafsdottir
- Department of Genetics and Molecular Medicine, Landspitali - National University Hospital, Hringbraut, 101, Reykjavik, Iceland
| | - G H Olafsdottir
- Icelandic Cancer Registry, Icelandic Cancer Society, Reykjavik, Iceland
| | - L Tryggvadottir
- Icelandic Cancer Registry, Icelandic Cancer Society, Reykjavik, Iceland.,Faculty of Medicine, Univ. of Iceland, Reykjavik, Iceland
| | - J J Jonsson
- Department of Genetics and Molecular Medicine, Landspitali - National University Hospital, Hringbraut, 101, Reykjavik, Iceland. .,Department of Biochemistry and Molecular Biology, Univ. of Iceland, Reykjavik, Iceland. .,Genetical Committee of the University of Iceland, Reykjavik, Iceland.
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Stefansdottir V, Skirton H, Jonasson K, Hardardottir H, Jonsson JJ. Effects of knowledge, education, and experience on acceptance of first trimester screening for chromosomal anomalies. Acta Obstet Gynecol Scand 2010; 89:931-8. [PMID: 20235896 DOI: 10.3109/00016341003686073] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVES To assess pregnant women's knowledge and understanding of first trimester prenatal screening (nuchal translucency, maternal serum free beta-human chorionic gonadotrophin and pregnancy-associated plasma-protein-A), to evaluate the impact of a new information booklet and investigate the effects of education and experiential knowledge of congenital disabilities on the perceived likelihood of accepting prenatal screening. DESIGN A quasi-experimental quantitative study with a self-completion questionnaire. SETTING Five different maternity care clinics in Iceland. POPULATION Expectant mothers in first trimester of pregnancy (n = 379). MATERIAL AND METHODS Expectant mothers were divided into two groups, an intervention and a control group, both receiving traditional care and information. The intervention group additionally received an information booklet about prenatal screening and diagnosis. MAIN OUTCOME MEASURES Women's knowledge score of prenatal screening. The correlation between education, knowledge score, experiential knowledge of congenital disabilities, and the likelihood of accepting prenatal screening. RESULTS More than half of the women (57%) believed they received sufficient information to make an informed decision about screening. Knowledge scores were significantly higher for the intervention group (with mean 4.8 compared with 3.7 on a 0-8 scale, p < 0.0001). Those with higher scores were more likely to accept screening (p < 0.0001). Women with experiential knowledge of congenital anomalies in their own families were more likely to accept prenatal screening (p = 0.017). CONCLUSIONS Various factors, e.g. experiential knowledge, education and information about prenatal screening affect the likelihood of participation in prenatal screening programs. More information results in better knowledge and higher uptake rate.
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Affiliation(s)
- Vigdis Stefansdottir
- Department of Genetics and Molecular Medicine, Landspitali University Hospital, Iceland
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Abstract
Laboratory Medicine organizations and their professional members have a goal and responsibility to benefit the health and wellbeing of the patients and communities they serve. Newer genetics and biochemical techniques raise significant issues of community concern, impacting on privacy, informed consent, access to and retention of samples and information. Balance may be required to ensure protection of individual rights against potential benefits to the broader community. While many national organizations may already have appropriate policies addressing various ethics issues, there is a need for an international framework to assist those nations that have not yet developed such policies, as well as to enable alignment of existing national policies. We have proposed a generic ethics framework, incorporating a hierarchy of four fundamental guiding principles: autonomy, justice, non-maleficence and beneficence. Proposals or issues requiring policy development can be considered and tested against this hierarchy, resulting in the development of policy and positions consistent with the above framework, acceptable to all participating stakeholders.
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Affiliation(s)
- Leslie Burnett
- Pacific Laboratory Medicine Services, Royal North Shore Hospital, and Northern Clinical School, University of Sydney, Sydney, Australia.
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Thorlaksdottir AY, Skuladottir GV, Petursdottir AL, Tryggvadottir L, Ogmundsdottir HM, Eyfjord JE, Jonsson JJ, Hardardottir I. Positive association between plasma antioxidant capacity and n−3 PUFA in red blood cells from women. Lipids 2006; 41:119-25. [PMID: 17707977 DOI: 10.1007/s11745-006-5079-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PUFA are susceptible to oxidation. However, the chain-reaction of lipid peroxidation can be interrupted by antioxidants. Whether an increased concentration of PUFA in the body leads to decreased antioxidant capacity and/or increased consumption of antioxidants is not known. To elucidate the relationship between plasma total antioxidant capacity (TAC), the concentration of antioxidant vitamins, and the proportion of PUFA in red blood cells (RBC), plasma TAC was measured by a Trolox equivalent antioxidant capacity assay in blood samples from 99 Icelandic women. Concentrations of tocopherols and carotenoids in the plasma were determined by HPLC, and the FA composition of RBC total lipids was analyzed by GC. Plasma TAC and the plasma concentration of alpha-tocopherol correlated positively with the proportion of total n-3 PUFA, 20:5n-3, and 22:6n-3 in RBC, whereas the plasma lycopene concentration correlated negatively with the proportion of total n-3 PUFA and 20:5n-3. On the other hand, plasma TAC correlated negatively with the proportion of n-6 PUFA in RBC. Plasma TAC also correlated positively with the plasma concentration of alpha-tocopherol, alcohol consumption, and age. Both the plasma concentration of alpha-tocopherol and age correlated positively with the proportion of n-3 PUFA in RBC; however, n-3 PUFA contributed independently to the correlation with plasma TAC. Because the proportion of n-3 PUFA in RBC reflects the consumption of n-3 PUFA, these results suggest that dietary n-3 PUFA do not have adverse effects on plasma TAC or the plasma concentration of most antioxidant vitamins.
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Affiliation(s)
- A Y Thorlaksdottir
- Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Iceland, Reykjavik, Iceland
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Abstract
Expression of iduronate-2-sulfatase (IDS) from three different promoters in four retroviral vectors was studied in peripheral blood lymphocytes from patients with Hunter syndrome (PBL(MPS)), i.e., the LTR in vectors L2SN and L2, avian beta-actin promoter in LB2, and the CMV early promoter in LNC2. PBL(MPS) were exposed to packaging cell supernatant resulting in transduction frequencies ranging 10-fold from 5 to 49%. Surprisingly, IDS activities were equally high in all transduced lymphocyte populations: 515 U/mg/h in PBL(MPS)-L2SN, 734 in PBL(MPS)-LB2, 352 in PBL(MPS)-L2, and 389 in PBL(MPS)-LNC2 compared to controls (<10 in PBL(MPS)-LXSN or PBL(MPS)). The half-life of endocytosed IDS in PBL(MPS) was 1.9 days. However, the level of lymphocyte IDS activity from proviral expression was found to be only a fraction of the total, a large portion being derived from reuptake of enzyme from murine packaging cells, i.e., a "second source" of enzyme. Therefore, measurement of transgene lysosomal enzyme soon after exposure of target cells to vector supernatant may yield a gross overestimate of long-term transgene expression by transduced cells. Nevertheless, patient fibroblasts cocultured with transduced PBL(MPS) had reduced (35)SO(4)-GAG accumulation, levels similar to those of normal fibroblasts. These studies revealed a broadly applicable phenomenon: cells can be charged with a lysosomal enzyme to levels much higher than those found in nature. By "supercharging" cells with a lysosomal protein (or other molecule bearing the mannose-6-phosphate ligand), such cells may be exploited as vehicles for systemic delivery of therapeutic or diagnostic agents.
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Affiliation(s)
- D Pan
- Gene Therapy Program, Department of Pediatrics, Institute of Human Genetics, University of Minnesota, 420 Delaware Street SE, Minneapolis, Minnesota, 55455, USA
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Jonsson JJ, Renieri A, Gallagher PG, Kashtan CE, Cherniske EM, Bruttini M, Piccini M, Vitelli F, Ballabio A, Pober BR. Alport syndrome, mental retardation, midface hypoplasia, and elliptocytosis: a new X linked contiguous gene deletion syndrome? J Med Genet 1998; 35:273-8. [PMID: 9598718 PMCID: PMC1051272 DOI: 10.1136/jmg.35.4.273] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
We describe a family with four members, a mother, two sons, and a daughter, who show clinical features consistent with X linked Alport syndrome. The two males presented with additional features including mental retardation, dysmorphic facies with marked midface hypoplasia, and elliptocytosis. The elliptocytosis was not associated with any detectable abnormalities in red cell membrane proteins; red cell membrane stability and rigidity was normal on ektacytometry. Molecular characterisation suggests a submicroscopic X chromosome deletion encompassing the entire COL4A5 gene. We propose that the additional abnormalities found in the affected males of this family are attributable to deletion or disruption of X linked recessive genes adjacent to the COL4A5 gene and that this constellation of findings may represent a new X linked contiguous gene deletion syndrome.
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Affiliation(s)
- J J Jonsson
- Department of Genetics, Yale University School of Medicine, New Haven, Connecticut 06520-8005, USA
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Piccini M, Vitelli F, Bruttini M, Pober BR, Jonsson JJ, Villanova M, Zollo M, Borsani G, Ballabio A, Renieri A. FACL4, a new gene encoding long-chain acyl-CoA synthetase 4, is deleted in a family with Alport syndrome, elliptocytosis, and mental retardation. Genomics 1998; 47:350-8. [PMID: 9480748 DOI: 10.1006/geno.1997.5104] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
We observed a family in which two boys were diagnosed with Alport syndrome, elliptocytosis, and mental retardation and carried a large deletion of the Xq22.3-q23 region, encompassing the COL4A5 gene. This suggests the possibility of a new contiguous gene syndrome. In an attempt to characterize the genes contributing to this complex phenotype, we have isolated a gene encoding a new long-chain acyl-CoA synthetase (FACL4 or LACS4) from the region deleted in these patients. Among several ESTs identified by searching the human gene map database maintained at the National Center for Biotechnology Information, using the map position as a query, only one was deleted in the patients. RACE products containing the entire ORF were subsequently generated. Northern blot analysis showed a 5-kb mRNA expressed in several tissues except for liver and lung. Brain shows a longer transcript, possibly reflecting the use of a brain-specific upstream ATG start codon. FACL4 encodes a predicted protein product of 670 amino acids (711 in brain), with a remarkable level of conservation compared to the rat acyl-CoA synthetases ACS4 and brain-specific ACS3 protein sequences. We are investigating the possibility that the absence of this enzyme may play a role in the development of mental retardation or other signs associated with Alport syndrome in the family.
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Affiliation(s)
- M Piccini
- Genetica Medica, Policlinco le Scotte, 53100 Siena, Italy
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Strathdee G, Sutherland R, Jonsson JJ, Sataloff R, Kohonen-Corish M, Grady D, Overhauser J. Molecular characterization of patients with 18q23 deletions. Am J Hum Genet 1997; 60:860-8. [PMID: 9106532 PMCID: PMC1712465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
The 18q- syndrome is a deletion syndrome that is characterized by mental retardation, hearing loss, midfacial hypoplasia, growth deficiency, and limb anomalies. Most patients with this syndrome have deletions from 18q21-qter. We report on three patients with deletions of 18q23. A mother and daughter with identical deletions of 18q23 have many of the typical features of the 18q- syndrome, including midfacial hypoplasia and hearing loss. In contrast, the third patient has few of the symptoms of the 18q- syndrome. A contig of the 18q23 region was generated to aid in the mapping of the breakpoints. FISH was used to map both breakpoints to the same YAC clone. Furthermore, somatic-cell hybrids from the daughter and the third patient were isolated. The mapping results of sequence-tagged sites relative to the two breakpoints were identical, suggesting that the two deletion breakpoints map very close to one another. The analyses of these patients demonstrate that the critical region for the 18q- syndrome maps to 18q23 but that a deletion of 18q23 does not always lead to the clinical features associated with the syndrome. These patients demonstrate the wide phenotypic variability associated with deletions of 18q.
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Affiliation(s)
- G Strathdee
- Department of Biochemistry, Thomas Jefferson University, Philadelphia, PA 19107, USA
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Braun SE, Pan D, Aronovich EL, Jonsson JJ, McIvor RS, Whitley CB. Preclinical studies of lymphocyte gene therapy for mild Hunter syndrome (mucopolysaccharidosis type II). Hum Gene Ther 1996; 7:283-90. [PMID: 8835216 DOI: 10.1089/hum.1996.7.3-283] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023] Open
Abstract
To explore the feasibility of ex vivo lymphocyte gene therapy for mild Hunter syndrome (mucopolysaccharidosis type II), we evaluated retrovirus-mediated gene transfer of the iduronate-2-sulfatase (IDS) coding sequence into peripheral blood lymphocytes from enzyme-deficient individuals (PBLMPS). Moloney murine leukemia virus-derived retroviral vectors were constructed by inserting the IDS cDNA under transcriptional regulation of the long terminal repeat (LTR) (in vector L2SN) or the cytomegalovirus (CMV) early promoter (vector LNC2). High-titer virus-producer cells were generated using amphotropic PA317 packaging cells. After 3 days of in vitro stimulation of T lymphocytes with anti-CD3 antibody and interleukin-2 (IL-2), PBLMPS were transduced once on each of the next 3 days. Seven to 21 days later, cultured PBLMPS were evaluated for gene transfer and IDS specific activity. Heterogeneous populations of L2SN-transduced PBLMPS had high levels of IDS enzyme activity (456 U/mg per hr +/- SD 292) despite a gene transfer efficiency of 5% or less. Owing to overexpression of IDS in that percentage of PBLMPS successfully transduced, IDS activity was increased above the deficiency found in patients with Hunter syndrome (< 20 U/mg per hr) to a level comparable with that of normal individuals (mean activity of uncultured normal leukocytes 807 U/mg per hr; SD 252). Reduced 35SO4-glucosaminoglycan (GAG) accumulation was observed in PBLMPS that had been transduced with L2SN, or when PBLMPS were grown in medium that had been "conditioned" by growth of L2SN-transduced cells. This latter result indicated that metabolic cross-correction occurred by means of intercellular enzyme transfer. These studies of retrovirus-mediated expression and metabolic correction, finding near-normal levels of IDS in cultured PBLMPS and metabolic correction, demonstrate the potential for treatment of mild, nonneuropathic Hunter syndrome by means of ex vivo lymphocyte gene therapy.
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Affiliation(s)
- S E Braun
- Department of Pediatrics, University of Minnesota, Minneapolis 55455, USA
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Abstract
We constructed and tested several retroviral vectors containing abbreviated purine nucleoside phosphorylase (PNP) genes in the reverse orientation, a strategy compatible with transduction of intron-containing genes. We observed two types of deletions in these vectors after one round of replication: (i) Deletions flanked by direct repeats with one copy of the repeat retained in the provirus, presumably resulting from reverse transcriptase slippage during (-) strand DNA synthesis. (ii) Deletions due to fortuitous splice sites in the PNP complementary strand. Two splice donor sites and three splice acceptor sites were identified in a 3.0-kb PNP minigene. We found that the splice donor sites (but not the splice acceptor sites) could be predicted by sequence analysis of the PNP complementary strand. To increase the frequency of intact PNP gene transduction, we introduced sequence modifications: The putative PNP polyadenylation signal and a truncated 117-bp 3' flank were recovered from a rearranged provirus and inserted in place of a 1.2-kb genomic 3' flank. Sequences associated with deletions were eliminated from the PNP 5' untranslated region, and two fortuitous splice donor signals in the complementary strand were inactivated. A retroviral vector LN-PMG11, containing the engineered 2.9-kb PNP minigene in the reverse orientation, was transduced intact in 23% (5/22) of clones after one round of replication and in 87% (20/23) of clones after a second round of replication from two primary virus producer clones. Directed mutagenesis of sequences preventing intact retroviral transduction thus provided a 2.9-kb PNP gene that was transduced intact and expressed at a high level.
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Affiliation(s)
- J J Jonsson
- Institute of Human Genetics, University of Minnesota, Minneapolis, MN 55455-0392, USA
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Jonsson JJ, Aronovich EL, Braun SE, Whitley CB. Molecular diagnosis of mucopolysaccharidosis type II (Hunter syndrome) by automated sequencing and computer-assisted interpretation: toward mutation mapping of the iduronate-2-sulfatase gene. Am J Hum Genet 1995; 56:597-607. [PMID: 7887413 PMCID: PMC1801163] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Virtually all mutations causing Hunter syndrome (mucopolysaccharidosis type II) are expected to be new mutations. Therefore, as a means of molecular diagnosis, we developed a rapid method to sequence the entire iduronate-2-sulfatase (IDS) coding region. PCR amplicons representing the IDS cDNA were sequenced with an automatic instrument, and output was analyzed by computer-assisted interpretation of tracings, using Staden programs on a Sun computer. Mutations were found in 10 of 11 patients studied. Unique missense mutations were identified in five patients: H229Y (685C-->T, severe phenotype); P358R (1073C-->G, severe); R468W (1402C-->T, mild); P469H (1406C-->A, mild); and Y523C (1568A-->G, mild). Non-sense mutations were identified in two patients: R172X (514C-->T, severe) and Q389X (1165C-->T, severe). Two other patients with severe disease had insertions of 1 and 14 bp, in exons 3 and 6, respectively. In another patient with severe disease, the predominant (> 95%) IDS message resulted from aberrant splicing, which skipped exon 3. In this last case, consensus sequences for splice sites in exon 3 were intact, but a 395 C-->G mutation was identified 24 bp upstream from the 3' splice site of exon 3. This mutation created a cryptic 5' splice site with a better consensus sequence for 5' splice sites than the natural 5' splice site of intron 3. A minor population of the IDS message was processed by using this cryptic splice site; however, no correctly spliced message was detected in leukocytes from this patient. The mutational topology of the IDS gene is presented.
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Affiliation(s)
- J J Jonsson
- Department of Pediatrics, University of Minnesota Medical School, Minneapolis 55455
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Affiliation(s)
- J J Jonsson
- Department of Genetics, Yale University, New Haven, CT 06520-8005
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Abstract
In previous studies characterizing intron-dependent expression of the human purine nucleoside phosphorylase-encoding gene (PNP), we identified a putative enhancer sequence in the first intron which was capable of mediating increased cat reporter gene expression in transfected murine NIH 3T3 cells in a position- and orientation-independent manner. In order to further characterize this enhancer activity, the nucleotide sequence was determined for the region of intron 1 to which this activity was originally ascribed. The sequence was analyzed for the presence of binding sites for known transcription factors, but none were identified. A 444-bp downstream portion of the intron-1 sequence enhanced cat expression either in conjunction with a human PNP promoter sequence or with a 105-bp heterologous herpes simplex virus thymidine kinase (TK) promoter. Nested deletions of the downstream intron-1 sequence fused to a TK::cat fusion gene localized the enhancer activity to a 170-bp sequence in intron 1. A 154-bp HgiAI fragment (bp 424 to 577 of intron 1) excised from this region contained enhancer activity which varied directly with the number of fragments inserted upstream from the TK::cat fusion gene. However, inversion of the HgiAI fragment in a PNP abbreviated gene, or relocation of the HgiAI fragment from intron 1 to a position upstream from the PNP promoter, reduced or eliminated PNP expression. The effect of the intron-1 enhancer element on PNP expression is thus maximized in a position- and orientation-dependent manner.
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Affiliation(s)
- J J Jonsson
- Institute of Human Genetics, University of Minnesota, Minneapolis 55455
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15
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Abstract
Abbreviated purine nucleoside phosphorylase (PNP) genes were engineered to determine the effect of introns on human PNP gene expression. PNP minigenes containing the first intron (complete or shortened from 2.9 kb down to 855 bp), the first two introns or all five PNP introns resulted in substantial human PNP isozyme expression after transient transfection of murine NIH 3T3 cells. Low level human PNP activity was observed after transfection with a PNP minigene containing the last three introns. An intronless PNP minigene construct containing the PNP cDNA fused to genomic flanking sequences resulted in undetectable human PNP activity. Heterogeneous, stable NIH 3T3 transfectants of intron-containing PNP minigenes (verified by Southern analysis), expressed high levels of PNP activity and contained appropriately processed 1.7 kb message visualized by northern analysis. Stable transfectants of the intronless PNP minigene (40-45 copies per haploid genome) contained no detectable human PNP isozyme or mRNA. Insertion of the 855 bp shortened intron 1 sequence in either orientation upstream or downstream of a chimeric PNP promoter-bacterial chloramphenicol acetyltransferase (CAT) gene resulted in a several-fold increase in CAT expression in comparison with the parental PNP-CAT construct. We conclude that human PNP gene expression at the mRNA and protein level is dependent on the presence of intronic sequences and that the level of PNP expression varies directly with the number of introns included. The disproportionately greatest effect of intron 1 can be explained by the presence of an enhancer-like element retained in the shortened 855 bp intron 1 sequence.
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Affiliation(s)
- J J Jonsson
- Institute of Human Genetics, University of Minnesota, Minneapolis 55455
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Jonsson JJ, McIvor RS. Herpes simplex virus thymidine kinase enzymatic assay in transient transfection experiments using thymidine kinase-deficient cells. Anal Biochem 1991; 199:232-7. [PMID: 1667455 DOI: 10.1016/0003-2697(91)90095-b] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
An enzymatic assay for herpes virus simplex type 1 thymidine kinase (HSV-TK) that was sensitive enough to quantitate intracellular levels of enzyme transiently expressed after transfection of HSV-TK vectors into TK-deficient cells using the DNA-calcium phosphate coprecipitation technique is described. TK activity in extracts of transfected cells was determined by binding of [methyl-3H]thymidylate product to thin layers of polyethyleneimine (PEI)-impregnated cellulose. The assay used high-specific-activity [methyl-3H]thymidine as substrate, which required removal of anionic material on a column of PEI-cellulose to enhance the signal-to-noise ratio. The assay was linear over a wide range with respect to the amount of HSV-TK plasmid transfected or content of HSV-TK enzyme in cell extracts. To validate the assay in transient expression experiments, HSV-TK and chloramphenicol acetyltransferase (CAT) plasmids were cotransfected into NIH/3T3 tk- fibroblasts. Transient TK and CAT levels were concordant in cell extracts prepared from replicate plates of transfected cells. Normalizing the transient TK activity for CAT activity from the cotransfected "internal standard" CAT plasmid improved precision significantly, reducing the sample-to-sample coefficient of variation from 41 to 19%. CAT normalization reduced experimental variability mostly by correcting outlying results in transfection efficiency. The HSV-TK reporter gene system based on TK enzymatic assay was thus subject to experimental variation similar to that of the well-established CAT reporter function, demonstrating its utility in transient gene expression analysis.
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Affiliation(s)
- J J Jonsson
- Department of Laboratory Medicine and Pathology, University of Minnesota, Minneapolis 55455
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Abstract
Purine nucleoside phosphorylase (PNP) is a ubiquitously expressed enzyme which contributes to the catabolism and recycling of nucleotides. To characterize the promoter region of the human PNP gene, the nucleotide sequence from a BamHI site located in the 5' untranslated region extending 2237 bp upstream to an XbaI site was determined. The transcriptional start site as determined by primer extension was 119 bp upstream of the coding sequence and consisted of a 5'-CA-3' dimer with A at +1. A TATA box was identified -24 to -29 bp upstream of the transcriptional start site. A CCAAT pentamer sequence in the inverted orientation was present at -51 to -55 bp and two GC rich regions were identified at -68 to -81 bp and -168 to -187 bp. Progressive 5' deletions of the 5' flanking region were fused to the chloramphenicol acetyltransferase (CAT) reporter gene and transient expression measured after transfection of murine NIH/3T3 fibroblasts. A 91 bp promoter (the shortest tested) provided CAT activity at 60% the level of a 216 bp promoter, possibly due to removal of the GC rich region between -168 and -187 bp. Longer promoters resulted in CAT expression at similar or lower levels than the 216 bp promoter indicating that this region contained all of the 5' flanking sequences affecting transcription from the PNP promoter.
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Affiliation(s)
- J J Jonsson
- Institute of Human Genetics, University of Minnesota, Minneapolis 55455
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Jonsson JJ, Johannesson GM, Sigfusson N, Magnusson B, Thjodleifsson B, Magnusson S. Prevalence of iron deficiency and iron overload in the adult Icelandic population. J Clin Epidemiol 1991; 44:1289-97. [PMID: 1753260 DOI: 10.1016/0895-4356(91)90090-v] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The aim of this cross-sectional study was to estimate the prevalence of iron deficiency and overload in the adult population in Iceland, a developed Scandinavian country. The study population consisted of 4240 individuals aged 25-74 years randomly selected from the national roster. Basic hematological, S-iron, S-total iron binding capacity (TIBC), and S-ferritin measurements were obtained on 2588 individuals (61.0%). The results indicated unusually large iron stores in the adult Icelandic population and significantly larger iron stores in the rural compared to the urban population. Iron deficiency was rare except in urban premenopausal women, where 1 in 4 showed evidence of iron deficiency and 3.2% had iron deficiency anemia. Seven patients with hereditary hemochromatosis were identified from a subgroup of 1887 subjects, resulting in a prevalence of 0.37%. Two of the hereditary hemochromatosis patients had been gastrectomized. Measures to improve the iron balance in urban premenopausal women cannot therefore include increased iron fortification of food but must be more directed towards the target group.
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Affiliation(s)
- J J Jonsson
- Department of Laboratory Medicine and Pathology, University of Minnesota Hospital and Clinic, Minneapolis 55455
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